1. Field of the Invention
The present invention relates to a fabric heating unit in crochet galloon looms, of the type comprising at least a heating element extending transversely to a fabric coming out of a crochet galloon loom and exhibiting an active surface designed to come in contact with said fabric and shielding means to reduce the heating action exerted on the fabric by the heating element.
2. Prior Art
It is know that fabrics produced by means of crochet galloon looms need to be submitted, before further workings, to dimensional stabilization treatments during which the fabric must undergo an appropriate heating.
The most conventional methods to carry out dimensional stabilization involve the use of specific equipments acting in a manner completely independent of the loom. With the use of these equipments the dimensional stabilization treatments clearly represent an additional working step to which the fabric must be submitted.
In order to eliminate this additional working step provision has been made for heating units directly mounted on the loom and acting so as to carry out the dimensional stabilization treatment as the fabric is being produced by the loom.
These heating units essentially comprise one or more heating elements consisting of cylindrical rollers heated by respective resistors and disposed so as to make the fabric slide thereon before it is wound around a reception cylinder.
While passing on said heating rollers the fabric undergoes an appropriate heating giving it the desired dimensional stabilization, with a more or less marked shrinkage.
Furthermore the resistor or resistors associated with each of said heating rollers are disposed eccentrically to the axis of the roller and therefore they are adjacent a localized area of the outer circumferential extension thereof. This area defines an active surface on which the fabric is obliged to slide during the normal working of the loom.
When for any reason the loom operation is stopped, the heating cylinders are automatically rotated through 180.degree. so that the fabric may rest on the surfaces thereof which are the farthest from the resistors and consequently less influenced by the heating action of said resistors.
In this manner the fabric does not run the risk of being overheated or burnt when its sliding on the heating cylinders is stopped.
Known heating units have some drawbacks. For example they consume a lot of energy due to the high amount of heat dissipated by the heating rollers which actually have an important mass with rather extended radiant surfaces.
The important mass of the heating rollers also involves long times to bring the latter to the appropriate exercise temperature during the loom starting steps after the loom has stopped for a long time.
Also due to the important mass of the rollers, it is necessary to use motors provided with high power in order to achieve the immediate rotations through 180.degree. of said rollers after each stopping and new operation of the loom.
It is also to be noted that, in spite of the resistors being disposed so as to accomplish a localized heating in specific areas of the rollers, an important amount of heat is also transmitted to the areas which are the farthest from said resistors. Under this situation, notwithstanding the rotation through 180.degree. performed by the heating rollers, when the loom stops an overheating of the fabric may occur, which will bring about a damage to the fabric above all when the latter is very delicate.
In addition, due to the fact that the fabric heating is only localized in specific areas of the roller, the fabric is often submitted to very high temperatures. Obviously, by effect of the fabric sliding, said high temperatures have a very short duration, but it would be better to submit the fabric to lower temperatures for longer times in order to achieve an optimal dimensional stabilization without running the risk of damaging the fabric.